Accessory Glands and Semen

Accessory Glands and Semen

During ejaculation, sperm pass through the ductus deferens and into the urethraThe tube that carries urine from the bladder to the outside of the body.. Along the way, they are joined by fluids from three accessory glands. On this lateralAway from the midline of the body. view this structure on the posterior face of the bladderA muscular organ that stores urine before excretion. is one of the seminal vesicles.  This is the prostate surrounding the prostatic urethra and this little egg is the bulbourethral gland.  Once all of their fluids mix together with the sperm, we call the final product semen or seminal fluid.  Only 205% of semen is sperm.  In that small proportion there can be 50 -120 million sperm per milliliter of fluid.  Less than 25 million is considered infertility.

Seminal Vesicle

The seminal vesicles make 65-75% of the seminal fluid, or semen.  The seminal vesicles contribute fructose and citrate. These are converted into ATPThe energy currency of cells used for muscle contraction. by the mitochondria in the mid piece of the sperm. They also contribute prostaglandins. These stimulate smooth muscle contractions in both the male and female reproductive systems. They also inhibit the attack of female immunoglobulins(Ig) Antibodies: Proteins produced by the immune system to target specific antigens. on the sperm. 

Seminal vesicles create something called semenoglin.  This adds viscosityThe thickness or resistance to flow in a fluid, such as blood. to the semen preventing drainage from the vaginaThe muscular canal connecting the uterus to the external genitalia.. About 20 to 30 minutes post-ejaculation the prostate specific antigen liquefies semen.  We use PSA levels to screen for prostate cancer. 

Prostate

The prostate gland complete surrounds the urethra, as shown in this picture.  This gland, which swells later in life as testosterone drops, contributes about 20-30% of semen contents. Semenoglin, made by the seminal vesicle is activated by an enzyme from the prostate called the presemenoglin.

Bulbourethra

Finally, the bulbourethral glands release  what is called the pre-ejaculatory fluid.  This contains buffersSubstances that resist changes in pH., mostly bicarbonate(HCO₃⁻) – A crucial buffer in blood that helps maintain pH balance; formed when carbon dioxide and phosphate, to neutralize the acidity of the vagina.